The present invention relates to side skirts used on belt conveyors that transport free-flowing materials such as coal. A common problem associated with transport of free-flowing materials by belt conveyors is loss of material over the edges of the belt. Belt conveyors are many times xe2x80x9ctroughedxe2x80x9d (upwardly flexed along the edges) to prevent this problem; however, troughing is limited by the flexibility of the belt material and does not completely eliminate spillage from the belt. The side skirt is another mechanism used to prevent the conveyed material from falling off of the edges of the belt.
A side skirt is typically made of rubber or similar flexible material. The skirt is hung over the belt such that its bottom edge meets the top of the belt, thereby creating a seal to further prevent loss of materials over the edges of the belt. In one arrangement, pressure-producing arms positioned at predetermined intervals along the skirt are used to maintain a seal between the belt and the skirt. The arm is a curved blade that rotates about a fixed pivot point. The first end of the arm is held against the top of the skirt. A force is applied to the second end of the pressure arm so that the arm is rotated downwardly, forcing the first end against the top of the skirt. The pressure can be applied by a spring, weight, or other similar device.
Such an arrangement is taught in U.S. Pat. No. 5,913,404, issued on Jun. 22, 1999 to Houston Bowman. However, the arrangement has certain drawbacks. The belt must move in a given direction, for example from left to right, for the pivoting arms to act as pressure arms thereby creating a seal between the skirt and the belt to prevent spillage of conveyed material. If it becomes desirable to move the free-flowing material from right to left, the arms become floating arms and no such seal is created between the skirt and the belt.
Although pressure arms creating a seal between the skirt and the belt are generally preferred, the construction of some belts makes floating contact necessary. For example, some belts are pieced together with metal clamps, creating an abrupt rise and fall of the surface of the belt as it moves. When a pressure skirt is used with such a belt, it can become caught or jammed. It may become advantageous to have a floating skirt, regardless of the directional movement of the belt, to avoid a belt jam.
Thus, depending on the construction of the belt, it becomes desirable to create a skirt that has the ability to form a seal with the belt, or if desired to make floating contact, regardless of the direction in which the conveyed material must be moved.
The present invention employs a mechanism that can either cause a seal to be created between the skirt and the belt or allow the skirt to make floating contact with the belt regardless of the directional movement of the belt.
A plurality of arms is spaced at predetermined intervals along the length of the side wall of the belt conveyor frame. Each arm has a first end at its top that is pivotally attached to the conveyor frame and a second end at its bottom that is pivotally attached to the skirt. Each arm can be adjusted to at least two different positions. In one position, known as the first configuration, the arm inclines in a first direction. In the other position, known as the second configuration, the arm inclines in a second direction.
When the arms are in the first configuration, as the belt moves in a first direction (from left to right), the friction between the bottom edge of the skirt and the top of the belt, together with the force of gravity pushing the pivoting arms downward, create a seal between the belt and the skirt, keeping the conveyed material from being lost over the edges. In this case the arms can be described as pressure arms. If the belt is moved in the opposite direction (from right to left), the friction between the bottom edge of the skirt and the top edge of the belt, together with the positioning of the arms, keep the skirt from pressing down onto the belt. In this second configuration the skirt makes floating contact with the belt and the arms can be described as floating arms.
When the arms are placed in the second configuration, as the belt moves in the first direction (from left to right), the arms act as floating arms, causing the skirt to make floating contact with the belt. When the belt is moved in the opposite direction (from right to left), the arms act as pressure arms, creating a seal between the skirt and the belt. The multiple points of attachment allow the arms to act as pressure or floating arms thereby permitting a pressure seal or floating contact regardless of the direction the belt moves.
Because the arms rotate about pivotal points of attachment, as the skirt wears it moves downward under the force of gravity, thus maintaining the desired contact with the belt even when it becomes shorter.